Types

Over 250 different primary immunodeficiencies (PIDs) have been identified, with about 20 of these accounting for over 90 per cent of cases. This means that many conditions are extremely rare: indeed for some conditions, fewer than ten cases have been identified.

Classification of PIDs

Every two years an international committee of experts meets to revise and update this classification, adding new conditions and information on the genes that cause PIDs.

At present, PIDs are grouped or classified under eight major subcategories based on what cells or parts of the immune system are affected.